Use main.jsbundle in iOS template for production build (#22531)

Summary:
Default HelloWorld template for iOS doesn't make production main.jsbundle. This is little bit confusing in compare with Android building app when everything works one first run.

Make it seamless, reduce confuse.
Based on docs https://facebook.github.io/react-native/docs/running-on-device#3-configure-app-to-use-static-bundle

Fixes #22335
Fixes #18562
Pull Request resolved: https://github.com/facebook/react-native/pull/22531

Differential Revision: D13372773

Pulled By: cpojer

fbshipit-source-id: 888c675b7d11b1a323445e092ec9ff83924c42f4